Type I diabetic women face the constant challenge of trying to maintain normal blood glucose levels to avoid the long-term complications of diabetes. Menstrual cycle changes during the luteal phase may contribute to fluctuations in glucose levels but definitive recommendations for adjustments of insulin dosage are not available due to conflicting experimental data. Some studies suggest that premenstrual syndrome (PMS) may exacerbate menstrual cycle changes in insulin sensitivity. Proposed Study I is designed to determine if there are differences in insulin sensitivity between the two phases of the menstrual cycle in Type I diabetic women with and without PMS. Diabetics may be particularly susceptible to PMS since previous studies suggest that PMS is related to low serotonin levels and diabetes itself may lead to low serotonin levels. Selective serotonin re-uptake inhibitors (SSRI's) have been used to successfully treat PMS in nondiabetic populations. In Type 2 obese diabetics, SSRI's have been shown to have a glucose-lowering effect, independent of weight loss. To date, no study has examined the use of SSRI's for the treatment of PMS in diabetic women. Study 2 will examine the effects of an SSRI on insulin sensitivity and PMS symptoms in Type I diabetic women with PMS. Insulin sensitivity will be measured using the frequently sampled intravenous glucose tolerance test.